1. Field of the Invention
The invention relates to a stator, a manufacturing method of a stator, and a rotary electric machine provided with the stator. More particularly, the invention relates to an improvement of the structure of a conducting wire used in a polyphase stator coil.
2. Description of Related Art
A rotary electric machine includes a stator provided with a stator coil that generates a rotating magnetic field, and a rotor rotatably provided inside the stator. The rotor rotates by electromagnetic action operating between the rotating magnetic field of the stator and the rotor.
One type of conducting wire used for the stator coil described above has a circular cross-section. However, in order to increase the in-slot space factor of the stator coil, a flat wire that is a conducting wire with a rectangular cross-section is sometimes used instead of a conducting wire with a circular cross-section.
Japanese Patent Application Publication No. 2011-72052 (JP 2011-72052 A) describes a stator having a stator core in which slots are formed, and a stator coil formed by a flat wire coated with an insulating layer being wound in a distributed manner in the slots. With the flat wire described in JP 2011-72052 A, the insulating layer on a surface contacting an adjacent flat wire in the radial direction in the slots is thin, so the in-slot space factor of the stator coil is increased. In addition, the insulating layer of the surface that contacts the stator core is thick, so insulation performance is ensured.
Japanese Patent Application Publication No. 2011-72071 (JP 2011-72071 A) describes a stator having a stator core in which slots are formed, and a stator, coil formed by a flat wire coated with an insulated layer being wound in a distributed manner in the slots. With the flat wire described in JP 2011-72071 A, a surface is coated with an insulating layer, and a coil insulating portion is attached to a portion that is adjacent to a different phase coil at the coil end, so interphase insulation is ensured.
The flat wire that is adjacent in the radial direction in the same slot is the same phase, so the insulating layer is able to be made thin as long as it is thick enough to provide insulation performance that prevents a short between these flat wires, i.e., as long as it is thick enough to ensure interphase insulation. However, in a polyphase stator coil formed by the flat wire being wound, flat wires with different phases are adjacent to one another at coil end portions that are exposed from the slots, so the insulating layer of the flat wire must be of a thickness that takes into account the potential difference among phases, i.e., must be thick enough to ensure interphase insulation. Therefore, the entire flat wire is coated with a comparatively thick insulating layer that takes into account a high potential difference among different phases, and this insulating layer thickness ends up impeding improvement of the in-slot space factor of the stator coil, which is problematic. If improvement of the in-slot space factor of the stator coil is limited, a reduction in motor size and improvements in motor output characteristics cannot be expected.
One conceivable way of handling this is to attach a coil insulated portion corresponding to the interphase insulation only to a portion near an area between different-phase flat wires at the coil end, as in JP 2011-72071 A. However, a coil insulating member is a separate member that is different from the flat wire, so even if it is attached, there will end up being a gap between these members, so the insulation performance may end up decreasing. On one hand, if an attempt is made to improve adhesion between the two by eliminating this gap, assemblability in a coil insulating member attaching process may decrease. In addition, during attachment, the insulating layer applied to the flat wire may be damaged by a coil attaching member, and as a result, insulation performance may end up decreasing.